MOSCOW — Russian authorities arrested the only opposition mayor of a major city Wednesday for allegedly soliciting bribes and said they found vast sums of cash stashed in his apartment building.

The Investigative Committee in Yaroslavl, a city of about 590,000 some 250 kilometers (150 miles) east of Moscow, said that it arrested mayor Evgeny Urlashov and three of his deputies for allegedly demanding a bribe of 14 million rubles (about $420,000) from an unidentified contractor. Police later said that this was part of a total 45 million ruble bribe Urlashov and his deputies allegedly demanded from the contractor.

Footage of police in masks, camouflage and bulletproof vests raiding Urlashov's apartment and flicking through large piles of cash led Russian state TV news. Police said they found $500,000 in cash belonging to Urlashov that next door, the RIA Novosti news agency reported, as well as a further 20 million rubles that Urlashov's daughter had tried to hide there.

Urlashov, a member of billionaire New Jersey Nets owner Mikhail Prokhorov's Civic Platform party, was elected by a landslide last year as anger over corruption and mismanagement by the Kremlin-controlled United Russia party surged. He denied the charges to Russian journalists before being driven to the police station.

The Kremlin has sought to increase control over Russia's regions by introducing strict oversight measures in local elections and cracking down on troublesome figures in the provinces. Golos, an independent vote monitoring organization that found staggering ballot fraud in the last round of national elections, was forced to shut down last month under pressure from a new law dubbing it a "foreign agent."

About 50 mayors who beat United Russia candidates were forcibly removed from office and charged with crimes during Dmitry Medvedev's presidency from 2008 to 2012, according to figures published by political scientist Mikhail Tulsky on the Russkaya Planeta website.